According to TVLine, season nine is gonna be different. As in, the entire season will take place over the course of Barney and Robin's wedding weekend:

CBS entertainment president Nina Tassler has now confirmed for TVLine that Season 9's entire run will, in fact, span the wedding weekend and just the wedding weekend, as the comedy details "how each character, before Ted, meets the mother. So, they each meet her independently before he does."

Crazy! So that explains the time stamp at the beginning of the finale. I'm curious to see how this will play out, but so far, I'm into it and think it could really work. We'll get to know the mother gradually—as each character meets her—but we won't have to watch a season full of awkward, forced attempts to fold her into the group's dynamic.